ABSTRACT Objective This study aims to describe patterns, sources, and reasons for cannabis use among cancer patients during active treatment (+CDTX) compared to no-use during active treatment (−CDTX). Methods Data are from 385 surveys collected via REDCap during phase I of an ongoing study among adult cancer patients seen at an NCI-designated comprehensive cancer center within the last 5 years of treatment. A harmonized survey was created with 11 other NCI centers to assess cannabis use patterns, sources, and reasons for use. Sociodemographics and cancer details were also collected via self-report. Descriptive statistics were calculated and stratified by +/−CDTX. Chi-squared tests were conducted to compare...